This study will examine the biochemical mechanisms whereby three populations of human Fc receptor leucocytes (granulocytes, monocytes and K cells) carry out cytolysis to a variety of target cells including bacteria, fungi, normal and malignant target cells. The metabolic characteristics of these effector cells in ADCC and NK assays will be determined as well as their ability to generate oxygen radicals (via stimulation with phorbol myristate acetate) which can kill bacteria, fungi and target cells. The molecular species responsible for target cell damage will be determined as well as characterization of membrane lipid changes which occur during oxidant injury. Finally, effector cells from patients with selective enzyme deficiencies in oxygen metabolism will be examined for ADCC and NK cytotoxic function.